21112121221 has 2 divisors, whose sum is σ = 21112121222. Its totient is φ = 21112121220.

The previous prime is 21112121207. The next prime is 21112121231. The reversal of 21112121221 is 12212121112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17525788225 + 3586332996 = 132385^2 + 59886^2 .

It is a cyclic number.

It is not a de Polignac number, because 21112121221 - 2²¹ = 21110024069 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21112121195 and 21112121204.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21112121231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10556060610 + 10556060611.

It is an arithmetic number, because the mean of its divisors is an integer number (10556060611).

Almost surely, 2^21112121221 is an apocalyptic number.

It is an amenable number.

21112121221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21112121221 is an equidigital number, since it uses as much as digits as its factorization.

21112121221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32, while the sum is 16.

Adding to 21112121221 its reverse (12212121112), we get a palindrome (33324242333).

The spelling of 21112121221 in words is "twenty-one billion, one hundred twelve million, one hundred twenty-one thousand, two hundred twenty-one".